Color-stable beta-modification of a monoazo dye, a process for its preparation, and its use

Abstract

The present invention relates to the β-modification of the dye of the formula I ##STR1## to a process for its preparation, to its use, and to a dye preparation containing it.

We claim: 
     
       1. β-Modification of the dye of the formula I ##STR3## whose X-ray diffraction diagram (Cu-Kα radication) has the following lines at diffraction angles 2Θ (°):   ______________________________________                                    
Lines of high intensity:                                                  
                   11.57, 24.93, 28.09;                                   
Lines of medium intensity:                                                
                   8.23, 15.52, 18.85, 20.27;                             
Lines of low intensity:                                                   
                   13.99, 19.35, 21.45.                                   
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       2. Process for the preparation of the β-modification of the dye of the formula I given in claim 1, characterized in that the α-modification of the dye of the formula I is heated to temperatures from 50° to 150°. 
     
     
       3. Process according to claim 2, characterized in that the α-modification is heated while suspended in water. 
     
     
       4. Process according to claim 3, characterized in that the suspension which is formed in the synthesis of the dye by diazotisation and coupling, after the coupling reaction is complete, is used directly as aqueous suspension. 
     
     
       5. Process according to claim 3, characterized in that dispersants and/or emulsifiers and/or solvents are added to the suspension to be heated. 
     
     
       6. Process according to claim 2, characterised in that the α-modification is heated in the course of the customary conversion of the dye into a very finely divided form. 
     
     
       7. Dye preparation, characterized in that it contains the β-modification of the dye of the formula I given in claim 1. 
     
     
       8. Process of dyeing or printing shaped articles, such as fibres, fabrics and sheets made of synthetic or semi-synthetic materials or mixtures thereof with cellulose fibres with the β-modification of the dye of the formula I given in claim 1.